1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing a continuous length of molded surface fastener from a continuously ejected board-shaped base layer of thermoplastic resin on the front surface of which a plurality of coupling elements are formed and to the back surface of which a backing material is attached, and more particularly to a method and apparatus for manufacturing a molded surface fastener where the backing material is attached in a firm and efficient manner so as to give this invention a wide variety of applications.
2. Description of the Related Art
Surface fasteners which have coupling elements on both the front and the back of their base layers are disclosed in, for example, Japanese Patent Publication No. Sho 42-87459 and Japanese Utility Model Laid-Open Publication No. Sho 55-122612. In the double-sided surface fastener disclosed in Japanese Patent Publication No. Sho 42-87459, multifilament loops are woven into one side of a single sheet of woven fabric and monofilament loops are woven into the other side. After both sides have been heat set, each of the monofilament loops is cut partially off to form hook shapes so as the woven fabric will then have loops on one side and hooks on the other side. Resin is then applied to the base fabric to hold the hooks and loops in place.
In the double-sided surface fastener disclosed in Japanese Utility Model Laid-Open Publication No. Sho 55-122612, soft tape having fiber loops on one side and fiber hooks on the other side is used. However, it is not made clear in this publication exactly how the hooks and loops are fixed to the structure of the soft tape. As fiber is used for the coupling elements for the double-sided surface fastener in this publication also, it is assumed that either the same woven structure as was disclosed in the above Japanese Patent Publication No. Sho 42-87459, or a structure where individual fibers are planted in a flexible sheet was used.
On the other hand, in Japanese Patent Publication No. Hei 1-238805 a surface fastener is disclosed in which the base material and the coupling elements are molded from synthetic resin. Here, in order to make a double-sided surface fastener, a large number of rows of protruding mushroom shaped coupling elements are formed on the front surface of the base layer from the same material as the base layer, as is shown in FIG. 18 of the same publication. A large number of rows of protruding coupling elements with spherical heads are also formed on the back side as is shown in the same figures. The theory of the structure of the double-sided surface fastener in this publication is as follows. As becomes clear from the above specification, these surface fasteners can be formed by putting thin tapes having large numbers of coupling elements formed in row on them onto both sides of a common base material of sufficient width to form a surface fastener. Alternatively, these thin tapes could simply be stuck together with adhesive or adhesive resin to form a surface fastener of fixed width.
When manufacturing the surface fastener disclosed in Japanese Patent Publication No Hei. 1-238805, thin tape having a large number of protruding coupling elements along its length is either injection or press molded in a continuous or non-continuous manner. The necessary number of tapes are then placed side by side and then glued together by using, for example, an adhesive.
A further surface fastener is disclosed in Japanese Utility Model Laid-Open Publication No. Hei. 55-55602. Here, a fiber backing material which is, for example, a knitted or woven article, non-woven cloth or paper is fused onto the back surface of a surface fastener molded from synthetic resin which has a base layer with a large number of hooks formed in it.
In the same publication, the fiber backing material is pushed with a great deal of force against the molded body while the resin from which it is made is still molten and in this way a surface fastener is formed. However, the details of this manufacturing process are not disclosed.
With the fabric type of surface fastener disclosed in Japanese Patent Publication No. Sho. 42-87459, the combination of the degree of softness usually associated with fabrics and the softness of monofilaments means that the loops and hooks can be brought together and peeled away from each other in a very smooth manner. Furthermore, by putting the monofilaments which are to be made into hooks through a drawing process, even with just a small area of cut through surfaces a high degree of coupling strength and flexibility can be attained. Also, by increasing the hook density, it is possible to increase the coupling strength and make the item sufficiently durable when used repeatedly. It is, however, very difficult to reduce the production costs with this fabric type of surface fastener as this process consumes a large amount of material and requires a large number of manufacturing steps.
Also, as is made clear in the aforementioned publication, this kind of surface fastener where coupling elements are woven into both sides of a fabric type base differs from other common fabric type surface fasteners with coupling elements on their surfaces in that it is impossible to impregnate resin only into the base fabric when it is intended to hold the roots of the coupling elements protruding from both sides of the base fabric in place. Unfortunately, this resin cannot be restricted to just the fase fabric and unavoidably adheres to the coupling elements. It is therefore very difficult to fix them in a secure manner without making the coupling elements tough.
Also, it becomes clear from the publication that a very complicated manufacturing process is required to produce the kind of integrally molded type surface fastener which is disclosed in Japanese Patent Publication No. Hei 1-238805. This means that this kind of double-sided surface fastener cannot be produced efficiently and it becomes apparent from FIG. 18 in the same publication that a high level of productivity is nearly impossible.
In the aforementioned Japanese Utility Model Laid-Open Publication No. Hei 55-55602 a material backed surface fastener is also forwarded. Here, the fiber backing material is pushed with a great deal of force against the molded body while the resin from which it is made is still molten. Since there is a great temperature differential between the backing material and the molded body, the molten resin solidifies as soon as it comes in contact with the fiber material irrespective to their welding performance, so that the two items cannot be fused together effectively only by pressing them together.